1. Field of the Invention
The present invention relates to a throttle body having a fuel return passage.
2. Description of the Related Art
Conventional throttle bodies often have a throttle position sensor for detecting the opening of a throttle valve on the side of a bore of the throttle body. The throttle position sensor has a rotation shaft for operating a potentiometer. The throttle bodies have a connector for connecting the rotation shaft to one end of the rotation shaft on the side of the bore. Particularly, JP-A-2002-309968 discloses a structure having a housing for the connector to prevent adhesion of soil or water to the connector during driving of the vehicle, and a drain opening in the housing for discharging water accumulating in the housing to the outside.
However, for saddle type four wheel vehicles (e.g., four wheel buggies) that may drive on marshy or swampy ground, the drain opening may allow water to flow into the housing. Thus, a saddle type four wheel vehicle may have a closed drain opening which creates the possibility that fuel leaks gradually from the air intake passage of the throttle body to the housing and accumulates in the housing. In this case, the accumulated fuel may come into contact with the connector in the housing so that the throttle position sensor may not be able to detect a correct throttle opening.
In that respect, JP-A-2-7368 discloses a technique in which a fuel return passage is provided which connects the portion downstream from a control valve in a bypass passage that connects the upper stream and the lower stream of the throttle body and the portion upstream from a throttle valve in the throttle body, and the fuel accumulated in the bypass passage is returned to an air intake passage using a negative pressure in the air intake passage.
The technique described in JP-A-2-7368 may be applied to the above described throttle body including the throttle position sensor. Specifically, the throttle body may have a fuel return passage that communicates the housing with the portion of the air intake passage downstream from the throttle valve, and an air inflow passage that communicates the housing with the portion of the air intake passage upstream from the throttle valve.
However, the throttle body has a single piece structure, so that a relatively small pressure difference occurs in the air intake passage in the throttle body. This may increase the possibility that the fuel accumulated in the housing cannot be returned smoothly into the air intake passage even with the fuel return passage and air inflow passage. Especially, it is difficult that the fuel having a higher viscosity than water circulates under a small pressure difference.